1. Field of the Invention
This invention relates to a gas and liquid contact body and to sheets for forming a contact body. More particularly, this invention relates to a novel arrangement for securing together corrugated sheets forming a contact body. Contact bodies frequently are used as fill for promoting heat transfer or heat and mass transfer from a liquid, such as water, to a concurrent-flowing, cross-flowing or counter-flowing gas, such as air. The contact bodies of the present invention are useful as fill for cooling towers, media for evaporative cooling, media for trickling filters for promoting biological oxidation of contaminants and pollutants in water and waste water treatment, fill for gas scrubbers for reducing airborne pollution, and the like.
2. Description of The Prior Art
Contact bodies typically are used as fill materials which promote the intimate mixture of and heat exchange between two counter-flowing or cross-flowing fluid streams. Contact bodies for gas and liquids, which are composed of layers or sheets made with folds between sheets with channels or passageways penetrating through the contact body so formed, are known in the art. For example, U.S. Pat. No. 3,262,682 discloses contact bodies consisting of thin sheets or layers which are folded or corrugated and which are disposed vertically. The corrugations extend at an oblique angle relative to the horizontal plane. Alternate layers have corrugations positioned obliquely in one direction with adjacent layers having their corrugations extending in opposite directions. The sheets may be interconnected at the places of contact by means of an adhesive such as a phenolic aldehyde resin. In operation, a liquid, such as water to be cooled, is sprayed on top of the contact body and travels down through it by gravity. A counter current of air is blown into or sucked through the open ends of the corrugations on one side of the contact body. Preferably, the layers or sheets are liquid- or water-absorbing and may be made of fibers of cellulose or an inorganic material such as asbestos. The sheets may also be made of a rigid plastic material such as unplasticized polyvinylchloride.
U.S. Pat. No. 3,599,943 discloses another gas and liquid contact body made of corrugated sheets. Each adjacent sheet has oppositely angled oblique major corrugations. The sheets are held together by rods passing through slots formed near the edges of the sheets.
U.S. Pat. No. 3,963,810 discloses a contact body comprising contact plates which may be provided with a plurality of spacer members protruding from opposite faces of the contact plate (FIG. 4). The contact plates are arranged so that the spacer members of adjacent contact plates contact one another permitting the contact plates to be stacked such that the corrugations of adjacent sheets do not contact one another.
U.S. Pat. No. 2,977,103 discloses cooling plates or baffles having a series of spaced parallel ribs of arcuate cross section and having a plurality of protuberances arranged in transverse and longitudinal rows on the plate which serve to space and separate adjacent plates from one another. To prevent the protuberances of one plate from nesting with the protuberances of adjacent plates, alignment lugs are provided which project a greater distance from the surface of sheet than the protuberances, whereby, the convex portions of the lugs will nest within the concave depressions of the lugs of an adjacent plate. The protuberances and aligning lugs may be on the same side of the sheet or may be located on both sides if desired.
U.S. Pat. No. 3,540,702 teaches a packing material formed from sheets which are joined by projecting seats. The outwardly projecting joint seats are formed at the apex portion of the largest scale bend or corrugation of these multiwave sheets. The outermost surfaces of the seats may be attached to one another by welding or adhesive.
U.S. Pat. No. 3,260,511 discloses packing media made from adjacent alternating corrugated sheets and intermediate flat sheets which may be joined together by means such as pinning, cementing, high frequency welding, clamping or similar devices. For example, they may be held together by a press stud molded or otherwise formed on the peak of one corrugated sheet engaged with a corresponding hole formed in the peak of an adjacent corrugated sheet passing through a hole punched or otherwise formed in an intermediate flat sheet. The stud may have a frustoconical shape with a larger diameter at the butt end, or alternatively, the butt may have a larger diameter than the stud itself (FIG. 3A). Alternatively, the structure may be constructed with a stud formed on the peak of one corrugated sheet threaded through a corresponding hole in the flat sheet and cemented to a recessed butt formed on the peak of an adjacent corrugated sheet facing the opposite surface of the flat sheet.
U.S. Pat. No. 3,281,307 discloses packing media which is composed of a bundle of corrugated sheets having protuberances formed on the peaks and troughs of the corrugations such that each of the protuberances on the peaks of the corrugations interfit with the rear of the protuberances on the trough of an adjacent sheet. The interfitted protuberances may be adhesively bonded or heat sealed together.
U.S. Pat. No. 3,475,012 discloses a gas liquid contact unit comprising a stack of sheets wherein each sheet has a plurality of hollows and protuberances molded in it with respect to the medial plane in the sheet, the hollows and protuberances having the shape of a frustum of a pyramid or cone, the top faces of the protuberances in one sheet registering with the top faces of the protuberances in an adjacent sheet.
U.S. Pat. No. 3,830,684 discloses corrugated sheets for liquid and gas contact apparatus. The corrugated sheet has a plurality of ramp-like deformations which reduce liquid channelling and which contact flat sheets interspersed between the corrugated sheets.
U.S. Pat. No. 3,965,225 discloses spacer-turbulators for use in separating corrugated-type fill sheets used in cross flow cooling towers and for imparting turbulence to the air flowing through the fill. The spacer turbulator comprises raised mounds for maintaining each fill sheet apart from an adjoining sheet where the mound contacts the fill sheet at the base of the concave portion of the fill sheet and contacts the adjoining fill sheet at the base of its concave portion.
U.S. Pat. No. 2,793,017 discloses corrugated sheet elements which are reinforced by spaced ribs disposed transversely of the sheet and projecting from at least one face a distance less than the amplitude of a corrugation such that the ribs serve as spacers between the assembled elements. Cup-like indentations may be provided in each of the ribs, and a smaller indentation in the troughs of the corresponding corrugation in the next adjacent sheet, such that the indentations in the corrugation mate with the cups and the ribs. The cups may be filled with adhesive for bonding the sheets together.
U.S. Pat. No. 3,574,103 discloses a laminated cellular material form being a plurality of corrugated sheet elements in which apical portions in at least one side of one sheet are notched to receive apical portions of the corrugations of a second sheet oriented in a transverse relation. The sheets may be adhesively bonded together where they contact each other. When bonded, the cellular core material may be used as packing for heat exchanger cores.
U.S. Pat. No. 3,733,063 illustrates and describes cooling tower packing assemblies in which sheets include knobs and plateaus acting as spacing elements. Although the sheets may be shipped in a nested condition, when they are assembled, the sheets are rotated 180 degrees and the knobs are bonded to the plateaus of the next adjacent sheet.
U.S. Pat. No. 2,940,736 illustrates and describes a set of plates for use in heat exchangers. Alternating plates have walls extending perpendicular to the surface of the sheet such that, when the wall-bearing sheets are packed alternately with relatively flat sheets, channels are formed. The channels direct the flow of the fluid media through the heat exchanger structure. The surface of at least every second plate in a stack making up a heat exchanger structure has a surface which is formed to promote heat transfer without unduly raising the pressure drop of gas flowing through the heat exchanger. This is accomplished by providing a multiplicity of shallow depressions and projections on the surface of the plate. Each of at least every second plate in a stack has a surface having a multiplicity of parallel furrows extending obliquely with respect to the longitudinal axis of the channels which define the general direction of the flow of the gaseous media through the heat exchanger. The crest forming ridges between the furrows are periodically interrupted by depressions to break up the laminar flow of gaseous media in the vicinity of the plates in order to promote the heat transfer. However, as shown, for example in FIG. 7, the stack is assembled without regard to the relative positions of the depressions in adjacent plates, the plates being spaced by the walls of the channels formed in every other plate in the stack.
Prior art contact bodies which are assembled from a plurality of parallel and generally vertical contact sheets, having a plurality of parallel corrugations forming alternating apices in the contact sheets, and oriented such that the corrugations are disposed at an angle to the horizontal and such that the corrugations of adjacent sheets intercept one another, suffer from several disadvantages. For example, because the adjacent sheets of such prior art contact bodies are bonded together at the apices of the intersections of the corrugations of adjacent sheets, and no special effort has been made in the prior art to position these intersections with reference to the edges of the contact sheets, on the average, few intersections occur near the edges of the contact sheets. Thus, the intersections, which are the sites at which the adjacent sheets are bonded together, occur substantially only within the interior of the contact body. As a result, the edges of the contact body disposed toward the incoming fluid streams to be contacted often present an irregular cross section to the incoming fluid streams.
This irregularity may result from the inability to position alternating sheets in precisely the same orientation during assembly of the contact body, from damage to the edges of the contact body or its component sheets occuring during shipping of the sheets, or assembly or installation of the contact body, or from damage to the edges of the contact body occurring during use of the contact body. In any case, the irregular cross section presented by the edges decreases the efficiency of the contact body because the incoming streams of fluid are nonuniformly distributed through the contact body.
Further, the incoming fluid streams may cause the edges of these prior art contact bodies to vibrate. These edge vibrations may ultimately result in material fatigue, delamination of the contact sheets, bending of the edges, wear of the edges, and/or breakage of the edges of the contact sheets. Clearly, there is a need for a means for securing the edges of such contact bodies to increase the operational efficiency and life expectancy of the contact bodies.
Conventionally, in corrugated fill media having no special protuberances, spacer members, indentations, and the like, adhesive or solvent is applied to the apices of the corrugations on one side of a sheet by conventional application means such as a roller; and the next adjacent sheet is laid atop the first sheet such that the corrugations of the two sheets cross. The apex of the corrugations may be slightly flattened to provide an enlarged bonding surface. When the sheets are thermo-formed from unplasticized polyvinylchloride, a solvent may be used to weld together the apical contacting portions of the corrugations on each of the sheets. Residual solvent is allowed to evaporate from the non-contacting portions of the sheets.
This assembly procedure has the disadvantage that it exposes a substantial proportion of the entire sheet surface, and in particular, the apices of the corrugations to the adhesive solvents which are employed to attack and fuse the sheet material together. The solvent exposure tends to embrittle and prematurely degrade synthetic polymeric materials, such as polyvinylchloride. This is undesirable.